November 28
The Winking Demon
Sun Position
The Sun is in Sagittarius at about -22° declination. In the Northern Hemisphere, this week often contains the earliest sunsets of the calendar year at mid-latitudes (though the winter solstice is still three weeks away). Southern Hemisphere days are long and warm.
Sky Highlight
Perseus is overhead from northern mid-latitudes on late November evenings, an ideal time to watch Algol through the night and catch its dimming cycle. Algol's period is 2.87 days, so with a chart of predicted minima (available from the AAVSO) you can know in advance when to watch. The fading takes about five hours and is detectable with the naked eye.
Deep Sky Object
M76, the Little Dumbbell Nebula, planetary nebula in Perseus, about 2,500 light-years away. One of the fainter Messier objects, but with Perseus overhead it is as accessible as it will be all year. The two-lobed shape earned it the nickname; a six-inch or larger telescope reveals the structure well. Best from northern latitudes.
Featured Star
Algol (β Persei) is an eclipsing binary system 92.8 light-years away (spectral class B8V + K2IV) and its brightness drops by about 1.3 magnitudes every 2.87 days when the dimmer K subgiant transits the brighter B star. The Arabs named it Rā's al-Ghūl, the Demon's Head; whether they noticed its variability is debated, but the name suggests long familiarity with something unsettling about it.
Around This Date
- November 28, 1659Christiaan Huygens made his earliest systematic drawings of Martian surface features, becoming the first to record and date surface detail on Mars.
- November 30, 1954Ann Hodges of Sylacauga, Alabama, was struck by a meteorite that broke through her roof, the only documented case of a meteorite injuring a person in the United States.
Algol's dimming is slow enough to watch in real time, a transit in progress, the demon's eye closing over a few hours before reopening at full brightness.